1. Field of the Invention
This invention relates generally to bearings for turbochargers. More particularly, the invention provides an integrated bearing system with journal and thrust bearings incorporated in a single unit centrally pinned to the bearing housing and having integral thrust surface and journal surface lubrication grooves in combination with turbine and compressor wheel thrust surfaces.
2. Description of the Related Art
Exhaust gas driven turbochargers include a rotating shaft carrying turbine wheel and a compressor wheel, which is rotatably supported within a center housing by oil lubricated bearings. The turbine wheel is driven by the exhaust gas at high rotational speeds, often in excess of 100,000 RPM, to drive the compressor wheel to provide boosted charge air for use by an internal combustion engine. Axial motion of the shaft and wheels must be resisted by the bearing system and rotational dynamics of the rotor group accommodated and damped by journal action of the bearing system.
Prior art systems typically employ a pair of journal bearings separately constrained or separated by a central spacer, to achieve desired rotational dynamics. Thrust loads are absorbed through conventional thrust washer or collar and end plate or flange designs, one element of which may be integrated with one of the journal bearings.
It is, therefore, desirable to provide a bearing system employing the minimum number of parts for simplicity. It is also desirable that the number of mating surfaces be reduced in the bearing system to improve normality and ease of balancing. It is further desirable that the bearing maintain angular flexibility to accommodate shaft motion while providing adequate damping. It is additionally desirable that the bearing include an integral pressure fed lubrication capability for thrust and journal surfaces.